Alkaline treatment of polyethylene terephthalate filaments or staple fibers to improve processing in textile machines and filaments produced thereby



HO(CH OI-l wherein n is an integer sive, 'as described in US. Patent No. 2,465,319. The "commercial type of polyester fiber disclosed in the just referred to. patent is'derived from the polymer of polythrough a spinneret.

drawingoperationor a similar process that orients the "yarn to give it high strength. shrinkage thereof, the filaments are stabilized, or heat set,

' terephthalate to an thereof and to produce noveltyelfects therein. In the thalate were spun into yarn, ning thereof were encountered during the handling of the staple fibers trapped between The present invention relates to the chemical modification of textile fibers and more particularly to improving the processability of polyester staple fibers by means of an alkaline treatment.

The fibers with which the present invention is concerned may be composed in general of fiber-forming polyesters that are chemically reactive with alkaline solutions and include particularly polyalky-lene terephthalates and-a glycol of the series from 2-10, incluprepa'red from terephthalic acid which is meltspun into filaments The filaments are subjected to a ethylene terephthalate,

Additionally, to reduce the as it is also termed, which consists essentially in exposing the filaments to a temperature higher than in subsequent processing or use. The heat setting operation to impart dimension stability to the filaments may be conducted either with aydry or wet heat and is usually required to prevent shrinkage during dyeing of the filaments.

to subject fabric made of polyethylene alkali treatment to improve the hand It is I known known processes the polymeric polyethylene terephthalate is hydrolized to a substantial extent by a relatively strong alkaline solution. In view or the nature of such :treatment, certain physical properties, such as tenacity,

are sacrificedin order to obtain the desired effect.

fibers of polyethylene terephcertain difiiculties in the spin- Heretofore, when staple fibers on the card and in the combing machine. These have a tendency to become lodged or enthe needles ofthe card and the combs of the combing machine to such an extent that only after a comparatively short time these machines do not perform satisfactorily. These processing difliculties, it been found, are particularly objectionable in the processing of fibers from the polyesters mentioned above which have been previously heat set to obtain dimensional stability. Moreover, during winding and twisting of the sliver produced by the carding d especially during operations in which the sliver is exposed to elevated tempera- .tures, as may be thecase during drawing, unduly high stresses are present which often result in breakage of the jthread. The present invention is directed to overcome the .just discussed processing difiiculties of polyester staple fibers.v

An additional advantage of the present invention is 9 that the fibers and threads treated in the present manner have reducedinterfilamentary friction and glide easily along each other.

It is an object of the present invention to provide a method of improving the processability of polyester staple fibers on the card and in the combing machine without nited States Patent C i Patented Aug. 29, 1961 2 appreciably lowering the physical properties thereof, such as tensile strength.

Another object of the present invention is to provide polyester staple fibers which are characterized by improved processability on the card and in the combing machine.

Still further objects and advantages of the present invention will appear from. the following description and appended claims.

In accordance with the present invention, polyester filaments are first given a treatment in a dilute alkaline solution and thereafter rinsed with water before substantial hydrolysis of the filaments occurs but after sufiicient time has elapsed to chemically modify the surface of the filaments so as to impart therein improved processability when staple fibers thereof are spun into yarn. The treatment with the said alkaline solution may be effected either in a cold condition or at high temperatures, with the rate of the treatment depending upon the temperature, the concentration and the particular alkaline substance employed. Ordinarily, it is preferred to use a temperature of at least 60 C. The alkaline solution may beprepared from alkali-metal hydroxides, such as sodium or potassium hydroxide or trom alkali-metal salts of weak acids. Surface active agents as disclosed hereinbelow may be employed to accelerate the action of the alkaline treatment.

It has been found that when the alkaline solutionv is prepared from an alkali-metal hydroxide, it is necessary to use a relatively weak solution of not more than 1.0% hydroxide by weight and preferably from 02-08% by weight for the preferred treating temperature of at least 60 C. The precise concentration is, of course, dependprepare the alkaline solution from salts of an alkali metal base and a weak inorganic acid. Other salts derived from other inorganic strong bases may be used. In view of their cheapness and availability, salts derived from sodium hydroxide are preferred which include such compounds as sodium borate, sodium carbonate, sodium phosphate, sodium sulfide, sodium silicate and sodium hypochlorite. The concentration of the alkaline-salt solutions is usually higher than solutions containing hydroxide. For the purposes or the present invention when a salt solution is employed, the concentration for best results and economic reasons should generally be between 0.5- 10.0% by W i t The alkaline solution may be applied to the polyester filaments in a variety of ways. For example, staple fibers may be stirred in a b-atchwise manner in a bath ganic solvents suitable for the purpose of the present invention. After the treatment is complete but, of course, before substantial hydrolysis of the polyester fiber or thread occurs, the'treated material is washed free of the unreacted agent in a suitable manner, such as by spraydescribed above with a solution containing one or more bases of an alkali metal, it was surprisingly found that the speed and intensity of the action of the solution may be appreciably increased if, according to the present invention, the treating solution additionally contains at least one anion-active compound. A treating solution containing strong bases and cation-active substances are not suitable since the cation-active substances, it is thought, interact with the polyethylene terephthalate to form a non-polar salt which is soluble with the result that the fibers are undesirably hydrolyzed. Furthermore, it has been found that a treating solution containing strong bases and non-ionics are not satisfactory because the solubility thereof in strong bases is generally small and because soluble non-ionics do not enhance the reaction to a great extent.

Suitable anion-active compounds for use in a solution containing an alkali metal hydroxide include, for example, sodium and potassium salts of fatty acids, alkylaryl-sulfonates, fatty alcohol sulfates and sulfated fatty acid salts of diethanol amine. These surface anion-active compounds may be employed in various concentrations with best results obtainable at a concentration of not more than 1.0% by weight and preferably 0.2-0.5 by weight. Highly satisfactory results are obtained by treating the fibers for not more than ten minutes at 90-100 C. with an aqueous solution made alkaline with an alkali metal hydroxide and containing 0.3% by weight of sodium stearate or sodium oleate. After the polyester materials have been treated according to the present invention, they are washed and dried as described above.

There appears to be a rather significant difference between the use of surface-active agents with an alkali metal base and with a basic salt. In using basic salt, there is no marked difference between the use of cationactive, anion-active or non-ionic substances. However, the anion-active substances are preferred because of economic reasons.

Suitable surface active compounds for use in an alkaline salt solution include for example, quaternary ammonium compounds, (for example lauryl and stearyl trimethyl ammonium chloride), ethoxylated higher primary amines (for example compounds with the general formula wherein x+y is at least 5), salts of single amines and polyamines (for example lauryl amino acetate and stearyl acetyl diethylene amine), ethoxylated fatty acids (for example polyglycol stearate), ethoxylated fatty acid amides (for example stearic acid amido ethoxylate), ethoxylated fatty alcohols (for example lauryl alcohol ethoxylate), ethoxylated higher amines (for example lauryl amino ethoxylate), ethoxylated alkyl phenols (for example nonyl phenol ethoxylate), sodium and potassium salts of fatty acids, alkyl-aryl-sulfonates (for example the sodium salt of dibutyl naphthalene sulfonic acid), fatty alcohol sulfates (for example the sodium salt of oleyl alcohol sulfate) and sulf-ated fatty acid salts of diethanol amine (for example the sodium salt of stearic diethanol amido sulfate).

These surface-active compounds may be used in various concentrations with best results obtained at a con- 4 l centration of 02-08% by weight. Very good results are obtained by treating the polyester fibers or threads for at least two minutes at -95 C. with a 3-6% solution by weight of sodium phosphate which also contains 0.2% by weight of a sulfated secondary alcohol with 12 C-atoms in the molecule and available in the trade under the name Teepol which chemically is a sodium higher alkyl sulfate, a product of the type:

CH.O.SOsNa R1 Furthermore, satisfactory results are obtained by treating the polyester fibers or threads for at least five minutes at 7080 C. with a solution containing 0.2-2.0% by weight of sodium carbonate and about 0.5% by weight of sodium stealrate.

A further understanding of the invention Will be obtained from the following examples which are intended to be illustrative, but not limitative of the present invention, percentages being by weight unless otherwise specified.

Example I An aqueous solution containing 0.3% sodium hydroxide was prepared. Polyethylene terephthalate staple fibers having a denier of 2.9 and a length of mm. were stabilized by the action of steam at C. for a period of 20 minutes. A 25 kg. portion of these stabilized fibers was treated in a vessel filled with the prepared solution, 400 liters thereof being recirculated for 25 minutes at a temperature of 90 C. After this treatment excess hydroxide solution was removed; and the unreacted solution was then removed by rinsing in water. The fibers were dried and finished after the rinsing step according to the usual processes.

Slivers produced from the fibers so treated could be processed in drawing and combing machines without any of the difficulties described in the foregoing. Analysis of the treated fiber revealed that the treatment did not hydrolyze it to an appreciable extent. Slivers produced from fibers which had not been subjected to the alkaline solution treatment in the same manner as set forth immediately above could not be processed satisfactorily in the drawing and combing machines.

Example I] A 25 kg. portion of polyethylene terephthalate staple fibers stabilized by steam at 140 C. for 25 minutes was treated by pressing an aqueous alkaline solution containing 1.0% potassium hydroxide through the fibers for an appropriate period. Afted this treatment, excess hydroxide solution was removed and the unreacted solution was then removed by pressing water through the fibers for 20 minutes. The fibers were dried and finished after the rinsing step according to the usual processes.

Slivers produced from the fibers so treated did not have a tendency to stick to the combs of the combing machines whereas slivers which had not been subjected to the alkaline solution treatment had such a tendency.

Example III An aqueous alkaline solution containing 0.5% sodium hydroxide and 0.3% sodium oleate was prepared. Polyethylene terephthalate staple fibers having a denier of 2.9 and a length of 100 mm. were stabilized by the action of steam at C. for a period of 20 minutes. A 25 kg. portion of these stabilized fibers was treated by pressing the prepared alkaline solution at 90 C. through the fibers for 8 minutes. After this treatment, excess solution was removed and the unreacted solution was then removed by pressing water at 70 C. through the fibers for 25 minutes. Thereafter, the fibers were dried and finished according to the usual processes.

Slivers produced from the fiber so treated did not have a tendency to stick to the combs of the combing machines whereas slivers which had been subjected to the alkaline solution treatment had such a tendency.

Example IV the fibers were dried and finished according to the usual processesw a g The fibers' thus treated could be more satisfactorily processed in the usual carding, drawing and combing machines as compared with fibers not so treated.

7 Example V An aqueous alkaline solution containing 0.5 sodium carbonate and 0.5% sodium stearate was prepared. Polyethylene terephthalate staple fibers having a denier of 2.9 and a length of 100 mm. were stabilized by the action of steam at 135 C. for a period of 20 minutes. A 25 kg. portion of these stabilized fibers was treated in a vessel filled with the prepared alkaline solution, 400 liters thereof being recirculated for 10 minutes at a temperature of 70 C. After this treatment, excess solution was removed and the unreacted solution was then removed by rinsing in water. The fibers were thereafter dried and finished according to the usual processes.

The fibers thus treated could be processed in a combing machine without the processing diificulties encountered when combing the fibers which had not been subjected to the alkaline treatment of this example.

Example VI An aqueous alkaline solution containing 3.0% sodium phosphate and 0.5% sulfated secondary alcohol with 12 C atoms in the molecule and sold under the trade name of Teepol was prepared. A 25 kg. portion of fibers stabilized in Example V was treated by pressing the prepared alkaline solution at 95 C. through the fibers for 5 minutes. After this treatment, excess solution was removed and the unreacted solution was then removed by pressing water at 70 C. through the fibers for 20 minutes. Thereafter, the fibers were dried and finished according to the usual processes.

The fibers thus treated could be processed in the usual drawing and combing machines without the difficulties hereabove described.

Example VII A 25 kg. portion of fibers stabilized in Example V was treated by pressing an aqueous alkaline solution containing 5.0% sodium phosphate at 95 C. through the fibers for 130 minutes. After this treatment, excess solution was removed and the unreacted solution was then removed by pressing water through the fibers. Thereafter, the fibers were dried and finished according to the usual processes.

The fibers thus treated were fully comparable with those obtained in Example VI in their processability during subsequent spinning processes.

Example VIII A 25 kg. portion of fibers stabilized in Example V was treated by pressing an aqueous alkaline solution containing 1.0% sodium stearate at 95 C. through the fibers for 40 minutes. Thereafter, the fibers were rinsed, dried and finished.

The treated fibers exhibited a reduced tendency to stick to the combs of the combing machine ascompared with untreated fibers.

. 6 Example IX A moving bundle of stretched continuous multifilament polyethylene terephthalate threads, the filaments of which had a denier of 2.9 was sprayed in succession with an aqueous alkaline solution containing 5.0% sodium carbonate and 0.5% of the sodium salt of dibutyl naphthalene sulfonic acid at C. and then with hot water at 70 C. After these foregoing treatments, the bundle was directed through a crimping chamber and then cut into staple fibers with a length of mm. Thereafter, these staple fibers were stabilized for 30 minutes at C. with steam. The stabilized fibers were then dried and finished in the usual ways.

The treated fibers could be processed on the card and in the combing machine without the difficulties hereabove described.

While the invention has been described with particular reference to preferred methods of carrying out its practice, other embodiments will be apparent to those skilled in the art. It is therefore intended to limit the invention only by the scope of the appended claims.

What is claimed is:

1. A process for treating polyethylene terephthalate filaments, which consists essentially of the steps of impregnating said filaments with an aqueous solution of a compound selected from the group consisting of alkalimetal hydroxides and alkali-metal salts of weak inorganic acids, the concentration of the alkali-metal hydroxide in the aqueous solution being about 0.2 to 1.0% by weight and the concentration of the alkali-metal salt in the aqueous solution being about 0.5 to 10% by weight, and thereafter removing said aqueous solution before substantial hydrolysis of said filaments occurs but after sufi'icient treatment to impart to said filaments improved processability when said filaments are cut into staple fibers and the staple fibers are processed on carding, drawing and combing machines.

2. The process according to claim 1 wherein the solution is maintained at a temperature of at least 60 C. during treatment.

3. The process according to claim 1 wherein the alkali-metal of the alkali-metal hydroxides is selected from the group consisting of sodium and potassium.

4. The process. according to claim 1 wherein the alkali-metal salt of a weak acid is selected born the group consisting of sodium horate, sodium carbonate, sodium phosphate, sodium sulfide, sodium silicate and sodium hypochlorite.

5. A process for treating heat-stabilized polyethylene terephthalate staple fibers, which consists essentially of the steps of impregnating said staple fibers with an aqueous solution containing about 0.2 to 1% by weight of an alkali-metal hydroxide, and thereafter removing said aqueous solution before substantial hydrolysis of said staple fibers occurs but after sufficient treatment to impart to said staple fibers improved processabili-ty on carding, drawing and combing machines.

6. The process according to claim 5 wherein a surface active anionic wetting agent compound is added to the solution in the amount of 0.2-1.0% by weight.

7. A process for treating heat-stabilized polyethylene terephthalate staple fibers, which consists essentially of the steps of impregnating said staple fibers with an aqueous solution containing about 0.2 to 0.8% by weight of sodium hydroxide at a temperature of 90 to 100 C., and thereafter removing said aqueous solution by rinsing said staple fibers in water before substantial hydrolysis of said staple fibers occurs but after suflicient treatment to impart to said staple fibers improved processability on. the carding, drawing and combing machines.

8. A process for treating heat-stabilized polyethylene terephthalate staple fibers, which consists essentially of the steps of impregnating said staple fibers with an aqueous solution containing 0.2 to 0.5% by weight of sodium hydroxide and about 0.3% by weight of sodium oleate for at most minutes, and thereafter removing said aqueous solution by rinsing said staple fibers in hot water before substantial hydrolysis of said staple fibers occurs but after sufiicient treatment to impart to said filaments improved processability on the carding, drawing and combing machines.

9. A process for treating heat-stabilized polyethylene terephthalate staple fibers, which consists essentially of the steps of impregnating said staple fibers with an aqueous solution containing 0.5 to 10.0% by weight of an alkali-metal salt of a weak inorganic acid, and thereafter removing said aqueous solution before substantial hydrolysis of said staple fibers occurs but after sufiicient treatment to impart to said fibers improved processability on the carding, drawing and combing machines.

10. The process according to claim 9 wherein a surface active anionic wetting agent compound is added to the solution in the amount of 0.28.0% by Weight.

11. A process for treating polyethylene terephthalate filaments, which consists essentially of the steps of impregnating said filaments with an aqueous solution of a compound selected from the group consisting of alkalimetal hydroxides and alkali-metal salts of weak inorganic acids, the concentration of the alkali-metal hydroxide in the "aqueous solution being about 0.2 to 1.0% by weight and the concentration of the alkali-metal salt in the aqueous solution being about 0.5 to 10% by weight, removing said aqueous solution before substantial hydrolysis Olf said filaments occurs but after sufiicient treatment to impart to said filaments improved processability when said filaments are cut into staple fibers and the staple fibers are processed on carding, drawing and combing machines, cutting the so-treated filaments into staple fibers, and thereafter heat-stabilizing the staple fibers by treating the same for minutes at C. with steam. 12. A filament produced by the process of claim 1.

Du Pont: Textile Fibers, Technical Information, Bulletin D-76, March 1956. 

11. A PROCESS FOR TREATING POLYETHYLENE TEREPHTHALATE FILAMENTS, WHICH CONSISTS ESSENTIALLY OF THE STEPS OF IMPREGNATING SAID FILAMENTS WITH AN AQUEOUS SOLUTION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKALIMETAL HYDROXIDES AND ALKALI-METAL SALTS OF WEAK INORGANIC ACIDS, THE CONCENTRATION OF THE ALKALI-METAL HYDROXIDE IN THE AQUEOUS SOLUTION BEING ABOUT 0.2 TO 1.0% BY WEIGHT AND THE CONCENTRATION OF THE ALKALI-METAL SALT IN THE AQUEOUS SOLUTION BEING ABOUT 0.5 TO 10% BY WEIGHT, RE MOVING SAID AQUEOUS SOLUTION BEFORE SUBSTANTIAL HYDROLYSIS OF SAID FILAMENTS OCCURS BUT AFTER SUFFICIENT TREATMENT TO IMPART TO SAID FILAMENTS IMPROVED PROCESSABILITY WHEN SAID FILAMENTS ARE CUT INTO STAPLE FIBERS AND THE STAPLE FIBERS ARE PROCESSED ON CARDING, DRAWING AND COMBING MACHINES, CUTTING THE SO-TREATED FILAMENTS INTO STAPLE FIBERS, AND THEREAFTER HEAT-STABILIZING THE STAPLE FIBERS BY TREATING THE SAME FOR 30 MINUTES AT 140*C. WITH STEAM. 